Download presentation
Presentation is loading. Please wait.
Published bySirje Piho Modified over 6 years ago
1
Whose got Genes? Genes, Heredity, & DNA Baker 2003/2004
2
Write underlined! What are genes? Genes are a segment of DNA on a chromosome that controls a particular trait. Genes are located on the chromosomes in the nuclei. Each organims has a fixed number of chromosomes. Humans have 23 pairs (46) chromosomes. Genetics is the study of how traits are passed on from one generation to another Baker 2003/2004
3
So what is DNA? DNA is a complex molecule (polymer) found in all living things. The primary function of DNA is to store and transmit genetic information that tells cells which proteins to make and when to make them. Baker 2003/2004
4
DNA TRIVIA An idea about size:
An average cell nucleus is about 6 micrometers in diameter. The total length of the DNA in the human genome is 1.8 meters. There must be several levels of coiling and super coiling in DNA Baker 2003/2004
5
What is GENETICS? Genetics is the study of how traits are inherited through the interactions of genes. Baker 2003/2004
6
What is a GENE? The material that controls which traits are expressed in an organism Genes come in pairs and offspring inherit one copy of each gene from each parent Baker 2003/2004
7
Define the following terms:
Heredity Allele Trait Baker 2003/2004
8
Define HEREDITY The passing of traits from parent to offspring
Baker 2003/2004
9
Define ALLELE The different forms of a trait that a gene may have
One form of a gene Baker 2003/2004
10
Define TRAIT Ways of looking, thinking, or being
Traits that are genetic are passed down through the genes from parents to offspring Baker 2003/2004
11
Describe RECESSIVE A trait that is covered over, or dominated, by another form of that trait and seems to disappear Hidden when the other copy of the gene contains the dominant allele. A recessive allele shows up only when there is no dominant allele present Shown with a lower-case letter Baker 2003/2004
12
What is HOMOZYGOUS? Both alleles [forms of the gene] are the same
When offspring inherit two dominant genes, (one dominant gene from each parent) they are said to be homozygous dominant When offspring inherit two recessive genes, (one recessive gene from each parent) they are said to be homozygous recessive Baker 2003/2004
13
What is HETEROZYGOUS? When alleles occur in different forms
When offspring inherit one dominant gene and one recessive gene, they are said to be heterozygous Since the dominant gene will be expressed, they are said to be heterozygous dominant Baker 2003/2004
14
Describe DOMINANT A trait that covers over, or dominates, another form of that trait Trait that always shows up, even when only one of the two alleles is in the dominant form Shown by a capital letter Baker 2003/2004
15
Define GENOTYPE An organism's genetic makeup Baker 2003/2004
16
Outward physical appearance and behavior of an organism
Define PHENOTYPE Outward physical appearance and behavior of an organism Baker 2003/2004
17
What is a PUNNETT SQUARE?
A tool to predict the probability of certain traits in offspring that shows the different ways alleles can combine A way to show phenotype & genotype A chart that shows all the possible combinations of alleles that can result when genes are crossed Baker 2003/2004
18
What is a PUNNETT SQUARE?
Letters stand for dominant and recessive alleles An uppercase letter stands for a dominant allele Lowercase letters stand for recessive alleles Baker 2003/2004
19
Punnett Squares Sample Problem 1. In roses, red flowers are dominant over white flowers. What are the possible offspring when a homozygous red rose is crossed with a homozygous white rose. Baker 2003/2004
20
Generation 1 homozygous red rose = RR homozygous white rose = rr
Baker 2003/2004
21
Generation 2 homozygous red rose = RR heterozygous red rose = Rr
homozygous white rose = rr Baker 2003/2004
22
Generation 3 homozygous red rose = RR heterozygous red rose = Rr
homozygous white rose = rr Baker 2003/2004
23
List the 3 Principles of Heredity
Traits are controlled by alleles on chromosomes An allele’s effect is dominant or recessive When a pair of chromosomes separate during meiosis the different alleles for a trait move into separate sex cells Baker 2003/2004
24
References Slideshow adapted from Baker 2003/2004
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.